What are the rules?

Tree growing into lines

Trees close to powerlines can be dangerous and in stormy conditions will often cause interruptions to the power supply. In high winds falling trees and branches can break lines, causing fire and the risk of electrocution. Trees touching powerlines can cause damage to the Network, power failures and in some cases even death. During bad weather hundreds of people experience first hand just how dangerous trees can be and what happens when they grow into, or even near, powerlines. This is not a new issue and landowners with trees need to be aware of their responsibilities.

What are my responsibilities?

Keep trees trimed1. Know the regulations
The Electricity (Hazards from Trees) Regulations 2003 specify the exact distances trees and other vegetation must be kept away from power lines. These distances are dependent on the line voltage and are known as the Growth Limit Zone (GLZ) and Notice Zone (NOTZ).

2 Keep your trees trimmed
A tree is your responsibility if you own the land the tree is on. You are responsible for keeping trees trimmed so they don't encroach inside these zones, and although you are responsible for organising regular maintenance, you do not have to do it yourself. Trees and other vegetation within the GLZ can only ever be trimmed by electrically competent tree workers - DO NOT ATTEMPT THIS YOURSELF. The cost of the first vegetation clearance will be paid for by Northpower – unless the line is a private service line in which case the cost is that of the land owner - and after this, you can arrange for Northpower, or for some other qualified contractor authorised by Northpower, to do the work.

Clipping Zone

What is Growth Limit Zone?

The Growth Limit Zone (GLZ) is the minimum space surrounding any powerline that must be kept clear of trees and other vegetation. The size of this zone depends on the voltage of the power lines.

The tree in this illustration will need to be cut or trimmed because it encroaches the Growth Limit Zone.

The Notice Zone (NOTZ) extends one metre beyond the Growth Limit Zone. Should a tree encroach the Notice Zone, we may send a 'Hazard Warning Notice' advising you that the tree must not encroach the GLZ. Trees in the NOTZ can be pruned by tree owners, provided they have written authorisation from Northpower. Please contact Northpower to arrange this.

The following table shows the clearances needed for the power lines that have a span of up to 150 metres.

For Powerline spans up to 150 metres
VOLTAGE GROWTH LIMIT ZONE
Distance from any point on the lines or equipment
50kV 3m
33kV 2.5m
11kV 1.6m
400/230V 0.5m

Greater clearances than shown above are needed for lines with spans longer than 150 metres.

What can happen if I don't take responsibility?

1. Liability and Offences

Trimming trees

Northpower and tree owners must comply with the Tree Regulations 2003 or face penalties. Northpower is required under the Tree Regulations 2003 to advise tree owners of their obligations and the penalties for not meeting their obligations.

Tree owners who receive a Cut or Trim Notice are required to ensure that the tree(s) is cut or trimmed to outside the notice zone in the time specified in the notice. Tree owners must also advise Northpower of the time and location of this work at least three working days prior to the work being undertaken.

2. Penalties Apply
Tree owners who fail to comply with these requirements could be fined up to $10,000 plus up to $500 a day for continuing offences. In addition tree owners could also be liable for costs if Northpower lines or equipment are damaged by their tree(s).

How often does Northpower check my trees?

Northpower regularly conducts tree surveys and inspects their network lines as required by the regulations. Tree owners of any identified problems are then notified. In all cases it is the tree owners who decide the future of their tree(s), choosing to either trim or remove the trees(s). In some situations this tree work is done by Northpower at no cost to the land owner.

You can read more about Tree Owner Responsibilites in our Trees Regulations Notice.